Department of Nutrition, Exercise and Sport Science and Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark;
J Neurophysiol. 2014 Feb;111(4):746-54. doi: 10.1152/jn.00372.2013. Epub 2013 Nov 13.
It is still widely believed that exaggerated stretch reflexes and increased muscle tone in ankle plantar flexors contribute to reduced ankle joint movement during gait in children with cerebral palsy (CP). However, no study has directly measured stretch reflex activity during gait in these children. We investigated sensory feedback mechanisms during walking in 20 CP children and 41 control children. Stretch responses in plantar flexor muscles evoked in stance showed an age-related decline in control but not CP children. In swing the responses were abolished in control children, but significant responses were observed in 14 CP children. This was related to reduced activation of dorsiflexors in swing. Removal of sensory feedback in stance produced a drop in soleus activity of a similar size in control and CP children. Soleus activity was observed in swing to the same extent in control and CP children. Removal of sensory feedback in swing caused a larger drop in soleus activity in control children than in CP children. The lack of age-related decline in stretch reflexes and the inability to suppress reflexes in swing is likely related to lack of maturation of corticospinal control in CP children. Since soleus activity was not seen more frequently than in control children in swing and since sensory feedback did not contribute more to their soleus activity, spasticity is unlikely to contribute to foot drop and toe walking. We propose that altered central drive to the ankle muscles and increased passive muscle stiffness are the main causes of foot drop and toe walking.
人们仍然普遍认为，脑瘫儿童在行走时，踝关节跖屈肌的伸展反射亢进和肌张力增高，导致踝关节活动受限。然而，目前尚无研究直接测量这些儿童行走时的伸展反射活动。我们研究了 20 名脑瘫儿童和 41 名正常对照儿童在行走时的感觉反馈机制。在站立期，跖屈肌的伸展反应在对照组中随年龄增长而下降，但在脑瘫组中没有。在摆动期，对照组的反应消失，但在 14 名脑瘫儿童中观察到显著的反应。这与摆动期背屈肌激活减少有关。在站立期去除感觉反馈，会导致对照组和脑瘫组的比目鱼肌活动明显下降。在对照组和脑瘫组中，比目鱼肌在摆动期的活动程度相同。在摆动期去除感觉反馈，对照组比脑瘫组的比目鱼肌活动下降幅度更大。脑瘫儿童伸展反射没有随年龄增长而下降，也不能在摆动期抑制反射，这可能与皮质脊髓控制不成熟有关。由于在摆动期，脑瘫儿童比对照组更频繁地出现比目鱼肌活动，并且感觉反馈对他们的比目鱼肌活动没有更多贡献，因此痉挛不太可能导致足下垂和足尖行走。我们提出，踝关节肌肉的中枢驱动改变和被动肌肉僵硬增加是足下垂和足尖行走的主要原因。
